Solar battery, method for manufacturing solar battery, method for manufacturing solar cell module, and solar cell module

ABSTRACT

The present invention provides a solar battery including a solar cell; a wiring substrate having a wire to be electrically connected to an electrode provided in the solar cell; and an adhesive agent for adhering the solar cell and the wiring substrate to each other. The present invention also provides a method for manufacturing the solar battery, a method for manufacturing a solar cell module using the solar battery, and the solar cell module.

TECHNICAL FIELD

The present invention relates to a solar battery, a method formanufacturing a solar battery, a method for manufacturing a solar cellmodule, and a solar cell module, in particular, a solar battery in whichelectrodes of a solar cell and wires of a wiring substrate can beelectrically connected to each other at a low temperature readily toattain highly reliable connection therebetween and relatively goodelectric characteristics; a method for manufacturing the solar battery;a method for manufacturing a solar cell module using the solar battery;and the solar cell module.

BACKGROUND ART

In recent years, problems of exhaustion of energy resources and globalenvironmental issues such as increasing CO₂ in the atmosphere havedriven demands for development of clean energy. In particular,utilization of solar batteries for photovoltaic power generation hasbeen developed, been put into practical use, and been expanded as a newenergy source.

An exemplary mainstream solar battery of such solar batteries isconventionally a dual-side electrode type solar battery. In thedual-side electrode type solar battery, a monocrystalline orpolycrystalline silicon substrate has a light-receiving surface in whichan impurity of conductive type opposite to that of the silicon substrateis diffused to form a pa junction. Electrodes are formed on thelight-receiving surface and rear surface opposite thereto in the siliconsubstrate. In recent years, a so-called back-side electrode type solarbattery is being developed in which both p type electrodes and n typeelectrodes are formed in the rear surface of a silicon substrate.

For cost reduction of raw materials, silicon substrates are gettingthinner. However, as silicon substrates are getting thinner, solar cellsare getting thinner, which disadvantageously results in cracks in cellscaused upon operations for wiring the solar cells during fabrication ofsolar cell modules.

To solve such a problem, for example, Japanese Patent Laying-Open No.2005-340362 (Patent document 1) proposes a method for wiring solar cellsusing a wiring substrate configured to include a base material, andwires formed on the base material.

As such, the utilization of a wiring substrate for connections of solarcells is proposed, but it has not been put into practical use yet due tothe following problems.

First, in the case where electrodes of a solar cell and wires of awiring substrate are connected to each other via a solder, when ageneral lead-free solder (Sn—Ag—Cu-based solder or the like) is used,the solder needs to be heated to around 250° C. Where the solder needsto be heated to such a high temperature to connect the electrodes of thesolar cell and the wires of the wiring substrate to each other, stressis generated due to a difference in thermal expansion coefficientbetween the silicon substrate of the solar cell and the wire material ofthe wiring substrate during cooling after the high temperature heating,which results in a crack in the solar cell or decreased reliability inthe connection therebetween such as removal of the solar cell from thewiring substrate.

Further, when connecting electrodes of a solar cell to wires of a wiringsubstrate using a solder, it is necessary to perform a step of aligningand positioning the solar cell on the wiring substrate and thereafterheating them using a reflow furnace. However, this step is complicatedand a solar cell having a large surface area is likely to be displacedduring the reflow, resulting in frequent occurrence of poor connection.

Furthermore, as indicated by Japanese Patent Laying-Open No. 2005-175436(Patent document 2), it is considered to connect electrodes of a solarcell and wires of a wiring substrate using an ACE (AnisotropicConductive Film) instead of a solder, but the ACF is expensive, whichmakes it difficult to use the ACF for a solar cell having a largesurface area. In addition, the ACF have too large electric resistancefor a large current to flow therein, resulting in decreased electriccharacteristics of the solar battery such as F.F (Fill Factor).

Patent document 1: Japanese Patent Laying-Open No. 2005-340362

Patent document 2: Japanese Patent Laying-Open No. 2005-175436

DISCLOSURE OF THE INVENTION Problems To Be Solved By the Invention

In view of the above, an object of the present invention is to provide asolar battery in which electrodes of a solar cell and wires of a wiringsubstrate can be electrically connected to each other at a lowtemperature readily to attain highly reliable connection therebetweenand relatively good electric characteristics; a method for manufacturingthe solar battery; a method for manufacturing a solar cell module usingthe solar battery; and the solar cell module.

Means For Solving the Problems

The present invention provides a solar battery including a solar cell; awiring substrate having a wire to be electrically connected to anelectrode provided in the solar cell; and an adhesive agent for adheringthe solar cell and the wiring substrate to each other.

In the solar battery of the present invention, the wiring substrateincludes an insulative base material and the wire formed on theinsulative base material, the wire is formed of a conductive material,and the adhesive agent is disposed on the insulative base material in atleast a part of a region other than a region in which the wire isformed.

Further, in the solar battery of the present invention, the insulativebase material preferably includes at least one of polyethyleneterephthalate and polyethylene naphthalate. Further, in the solarbattery of the present invention, the insulative base material may alsoserve as a weather-resistant film.

Further, in the solar battery of the present invention, the wire ispreferably formed of a material including at least one selected from agroup consisting of copper, aluminum, and silver.

Further, in the solar battery of the present invention, the adhesiveagent preferably includes at least one selected from a group consistingof a silicone-based adhesive agent, an acrylic-based adhesive agent, anepoxy-based adhesive agent, and a rubber-based adhesive agent.

Further, in the solar battery of the present invention, the adhesiveagent preferably has stable adhesiveness even when exposed to anenvironment at a temperature of 150° C. or greater.

Further, in the solar battery of the present invention, the adhesiveagent is preferably a viscous adhesive agent.

Further, in the solar battery of the present invention, the solar cellis preferably a back-side electrode type solar cell.

Further, in the solar battery of the present invention, the electrode ofthe solar cell preferably has a shape of at least one of a strip and adot.

Further, in the solar battery of the present invention, the electrode ofthe solar cell and the wire of the wiring substrate may be electricallyconnected to each other via a conductive adhesive agent.

Here, in the solar battery of the present invention, the conductiveadhesive agent preferably has a melting temperature/hardeningtemperature of 180° C. or smaller.

Further, in the solar battery of the present invention, the conductiveadhesive agent preferably has an electric resistivity of 0.001Ω cm orsmaller.

Further, in the solar battery of the present invention, the conductiveadhesive agent is preferably an Sn—Bi-based solder.

Furthermore, the present invention provides a method for manufacturingthe solar battery, including the steps of: disposing a viscous adhesivelayer on a base material; disposing the wire on the viscous adhesivelayer; disposing the wire, disposed on the viscous adhesive layer, onthe adhesive agent disposed on the insulative base material; andremoving the wire from the viscous adhesive layer to transfer the wireonto the adhesive agent.

Furthermore, the present invention provides a method for manufacturingthe solar battery, including the steps of: applying the adhesive agentto at least one of the solar cell and the wiring substrate; and adheringthe solar cell and the wiring substrate using the adhesive agent. Here,the adhesive agent is applied using any of screen-printing, offsetprinting, inkjet printing, and a dispenser.

Furthermore, the present invention provides a method for manufacturing asolar cell module in which the solar battery is sealed in a sealingmaterial, wherein when sealing the solar battery, the electrode of thesolar cell and the wire of the wiring substrate are mechanicallycompressed and bonded.

Furthermore, the present invention provides a method for manufacturing asolar cell module in which the solar battery is sealed in a sealingmaterial, wherein when sealing the solar battery, the electrode of thesolar cell and the wire of the wiring substrate are mechanicallycompressed and bonded with the conductive adhesive agent interposedtherebetween.

Furthermore, the present invention provides a solar cell module in whichthe solar battery is sealed in a sealing material, wherein the sealingmaterial is contained in a container having, on at least one of itsbottom portion and its side wall, a moisture penetration preventinglayer for preventing penetration of moisture.

Effects of the Invention

According to the present invention, there can be provided an inexpensivesolar battery in which electrodes of a solar cell and wires of a wiringsubstrate are electrically connected to each other at a low temperaturereadily to attain highly reliable connection therebetween and relativelygood electric characteristics; a method for manufacturing a solar cellmodule using the solar battery; and the solar cell module.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross sectional view of one exemplary solarbattery of the present invention.

FIG. 2 is a schematic cross sectional view of one exemplary solarbattery of the present invention.

FIG. 3( a) is a schematic planar view of one exemplary rear surface ofthe solar cell used in the solar battery of the present invention. FIG.3( b) is a schematic planar view of another exemplary rear surface ofthe solar cell of the solar battery of the present invention.

FIG. 4 is a schematic planar view of one exemplary wiring substrate usedin the solar battery of the present invention.

FIGS. 5( a)-(c) are schematic cross sectional views each illustratingone exemplary method for fabricating the wiring substrate used in thesolar battery of the present invention.

FIG. 6 is a schematic planar view of one exemplary solar battery of thepresent invention.

FIG. 7 is a schematic planar view of another exemplary solar battery ofthe present invention.

FIGS. 8( a) and (b) are schematic cross sectional views eachillustrating one exemplary method for manufacturing the solar battery ofthe present invention.

FIG. 9 is a schematic cross sectional view of one exemplary solar cellmodule of the present invention.

DESCRIPTION OF THE REFERENCE SIGNS

100: solar cell; 101: silicon substrate; 102: anti-reflection film; 103:passivation film; 104: n type impurity doping region; 105: p typeimpurity doping region; 106: n electrode; 107: p electrode; 108:conductive adhesive agent; 109: wire for n type; 110: wire for p type;111: insulative substrate; 112: slit; 113: connection electrode; 114:busbar p electrode; 115: busbar n electrode; 116: conductive member;120: adhesive agent; 121: base material; 122: hardening resin; 124:transparent substrate; 125: sealing material; 126: insulative film; 127:metal film; 128: container; 200: wiring substrate.

BEST MODES FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described below. In thedrawings of the present invention, the same reference charactersindicate the same or equivalent portions.

FIG. 1 shows a schematic cross sectional view of one exemplary solarbattery of the present invention. The solar battery shown in FIG. 1 hassolar cells 100 and a wiring substrate 200. Each of solar cells 100 hasan n type or p type silicon substrate 101. Silicon substrate 101 has alight-receiving surface (surface of a side via which sunlight mainlyenter) on which an anti-reflection film 102 is formed and has a rearsurface (surface opposite to the light-receiving surface) in which ntype impurity doping regions 104 formed by diffusing an n type impurityand p type impurity doping regions 105 formed by diffusing a p typeimpurity are provided alternately with a predetermined spacetherebetween.

Provided on the rear surface of silicon substrate 101 is a passivationfilm 103. N electrodes 106 penetrating through contact holes formed inpassivation film 103 are formed to make contact with n type impuritydoping regions 104, and p electrode 107 penetrating therethrough areformed to make contact with p type impurity doping regions 105.

Wiring substrate 200 has an insulative substrate 111 as well as wiresfor n type 109 and wires for p type 110 both formed on insulativesubstrate 111.

Further, n electrodes 106 of solar cell 100 are electrically connectedto wires for n type 109 of wiring substrate 200, whereas p electrodes107 are electrically connected to wires for p type 110 of wiringsubstrate 200.

Here, a feature of the solar battery of the present invention lies inthat the connection between n electrodes 106 of solar cell 100 and wiresfor n type 109 of wiring substrate 200 and the connection between pelectrodes 107 and the wires for p type 110 of wiring substrate 200 areachieved through adhesion provided by an adhesive agent 120 betweensolar cell 100 and wiring substrate 200.

Since solar cell 100 and wiring substrate 200 are fixed to each other bymeans of the adhesion provided by adhesive agent 120 between solar cell100 and wiring substrate 200 as such, solar cell 100 can be fixed ontowiring substrate 200 only by aligning and disposing solar cell 100 onwiring substrate 200. Thereafter, for example, the solar battery thusobtained is sealed in a sealing material such as a resin to fabricate asolar cell module In this way, good electric connection throughmechanical compression bonding is achieved. By fabricating the solarcell module in this way, they are less likely to be displaced from eachother after the solar cell is placed on the wiring substrate using theadhesive agent. As such, the step of connecting using a solder, whichrequires heating at approximately 250° C., can be omitted, thus readilyrealizing highly reliable connection at a low temperature. Further,since n electrodes 106 of solar cell 100 and wires for n type 109 ofwiring substrate 200 are in direct contact with each other and pelectrodes 107 of solar cell 100 and wires for p type 110 of wiringsubstrate 200 are also in direct contact with each other, electricresistance at the connection portions can be reduced as compared withthe case where they are connected using an ACF, thereby achievingrelatively good electric characteristics of the solar battery such asF.F.

FIG. 2 shows a schematic cross sectional view of another exemplary solarbattery of the present invention. The solar battery shown in FIG. 2 isdifferent from the solar battery shown in FIG. 1 in that the connectionbetween n electrodes 106 of solar cell 100 and wires for n type 109 ofwiring substrate 200 and the connection between p electrodes 107 ofsolar cell 100 and wires for p type 110 of wiring substrate 200 areachieved using a conductive adhesive agent 108.

Also in the solar battery shown in FIG. 2, solar cell 100 and wiringsubstrate 200 are fixed to each other by adhesive agent 120 providedtherebetween. Where a solder is used as the conductive adhesive agent108, for example, conductive adhesive agent 108 may be provided andthereafter they may be heated in a reflow furnace and accordinglyconnected to each other.

In the solar battery shown in FIG. 2, it is very beneficial to use asconductive adhesive agent 108, for example, an Sn—Bi-based solder, whichhas a low melting point, is inexpensive, and has a low electricresistance. The Sn—-Bi-based solder is adhered in advance to at leastone of each electrode of solar cell 100 and each wire of wiringsubstrate 200, and solar cell 100 is placed on wiring substrate 200.Solar cell 100 and wiring substrate 200 are fixed to each other byadhesive agent 120. Thereafter, they are not heated in a reflow furnaceor the like, and are sealed in a sealing material as with thedescription above. The step of heating using a reflow furnace can beomitted because heat generated during the process of sealing andmechanical compression bonding provided by the sealing securely achieveelectric connection with conductive adhesive agent 108 interposedtherebetween. This holds true for a case where a conductive adhesiveagent of low-temperature hardening type (including a conductive adhesiveagent other than a solder) different from the Sn—-Bi-based solder isused as conductive adhesive agent 108.

For example, as shown in FIG. 1 and FIG. 2, by fixing solar cell 100 towiring substrate 200 using adhesive agent 120, the connection locationsof solar cell 100 and wiring substrate 200 can be prevented from beingdisplaced from each other during a period of time until the solarbattery is sealed in the sealing material to complete the fabrication ofthe solar cell module. In this way, highly reliable connection isachieved. Further, it can be expected to reinforce the connectionbetween solar cell 100 and wiring substrate 200 after the solar batteryis sealed.

As adhesive agent 120, any material can be used without a particularlimitation as long as it is capable of adhering solar cell 100 andwiring substrate 200 to each other. For example, a material usabletherefor is a material containing at least one selected from a groupconsisting of a silicone-based adhesive agent, an acrylic-based adhesiveagent, an epoxy-based adhesive agent, and a rubber-based adhesive agent,each of which has a high heat resistance. Here, the silicone-basedadhesive agent, the acrylic-based adhesive agent, the epoxy-basedadhesive agent, and the rubber-based adhesive agent that can be usedherein are, for example, conventionally known ones.

Further, it is preferable to use a viscous adhesive agent as adhesiveagent 120. When a viscous adhesive agent is used as adhesive agent 120,stress can be absorbed due to flexibility of the viscous adhesivematerial to avoid poor connection between solar cell 100 and wiringsubstrate 200. In addition, cracks in solar cell 100 are likely to beeffectively prevented. Further, even if the connection locations ofsolar cell 100 and wiring substrate 200 are displaced from each other,solar cell 100 and wiring substrate 200 can be detached from each otherand then can be connected again to each other, advantageously. It shouldbe noted that a viscous adhesive agent is one type of adhesive agent,which has viscosity in general, has fluidity against an adhered materialunder application of pressure, and has retention power provided byaggregation against removal instead of hardening.

Furthermore, in order to seal the solar battery, the solar battery needsto be heated. Hence, for adhesive agent 120, it is preferable to use anadhesive agent exhibiting stable adhesiveness even when exposed to anenvironment at a temperature of 150° C. or greater, and it is morepreferable to use one exhibiting stable adhesiveness even when exposedto an environment at a temperature of 180° C. or greater.

The “stable adhesiveness” described above indicates such adhesivenessthat provides viscosity even under application of heat and does notcause displacement of the solar cell and the wiring substrate even whenan impact such as vibration is applied. Further, the adhesive agentpreferably has stable adhesiveness after the heating, and preferablysecures the electric connection therebetween by adhering the solar celland the wiring substrate to each other.

Specifically, exemplary adhesive agents exhibiting stable adhesivenesswhen exposed to an environment at a temperature of 180° C. or greaterare SD4570, which is a silicone-based adhesive agent, provided by theDow Corning Corporation; 9079, which is an acrylic-based adhesive agent,provided by the Sumitomo 3M Limited.; C-1080A/B, which is an epoxy-basedadhesive agent, provided by the Nacalai Tesuque, Inc; and the like.Another exemplary adhesive agent is DB5441, which is a screen-printableacrylic-based adhesive agent (viscous adhesive agent), provided by theDiabond Industry co., Ltd, or the like, and can be patterned and formedon the base material of wiring substrate 200 and/or portions of solarcell 100 other than the electrodes. They exhibit stable adhesivenesseven when exposed to an environment at a temperature of 150° C. orgreater. Further, a viscous tape can be used which has a PET basematerial or PEN base material to which an adhesive agent (viscousadhesive agent) is applied in advance Examples thereof are PET tapeYT153S, which employs a PET base material and a silicone-based adhesiveagent, provided by the YOUNGWOO CO., LTD.; a tape No.754, which employsa PET base material and an acrylic-based adhesive agent, provided by theSumitomo 3M Limited; a tape No. 4734, which employs a PET base materialand a rubber-based adhesive agent, provided by the Sumitomo 3M Limited;and T4900, G9052, etc., which are acrylic-based viscous adhesive agents(double-sided tape), provided by the Sony Chemicals Corporation. Theseexhibit stable adhesiveness even when exposed to an environment at atemperature of 150° C. or greater.

Further, adhesive agent 120 is preferably provided in at least a portionof wiring substrate 200 other than the wires.

Furthermore, as insulative substrate 111 used for wiring substrate 200,for example, a substrate made of a material having an electricresistance higher than those of wires for n type 109 and wires for ptype 110 can be used. However, in the present invention, since theelectrodes of solar cell 100 and the wires of wiring substrate 200 canbe connected to each other at a low temperature, it is preferable to usePEN (polyethylene naphthalate) and/or PET (polyethylene terephthalate)therefor. When PEN or PET is used as insulative substrate 111 of wiringsubstrate 200, its material cost is not so expensive, whereby the costof manufacturing the solar battery is likely to be reduced.

As wires for n type 1.09 and wires for p type 110 used in wiringsubstrate 200, any material can be used without a particular limitationas long as it is made of a conductive material. However, for furtherreduction in electric resistance of the wires, they are preferablyformed of a material including at least one selected from a groupconsisting of copper, aluminum, and silver. It should be noted thatwires for n type 109 and wires for p type 110 may be formed of the samematerial or different materials.

As conductive adhesive agent 108, for example, agents made of aconductive material can be used. Among them, it is preferable to use onehaving its melting temperature or hardening temperature of 180° C. orsmaller, more preferably, of 150° C. or smaller. For simplification ofsteps, conductive adhesive agent 108 is preferably melted or hardened inthe step of sealing the solar battery because the step of sealing isnormally performed at a temperature of 180° C. or smaller. Furthermore,when conductive adhesive agent 108 has a melting temperature orhardening temperature of 180° C. or smaller and for example a PEN filmis used for insulative substrate 111 of wiring substrate 200, insulativesubstrate 111 is hardly shrunk by heat. Likewise, when conductiveadhesive agent 108 has a melting temperature or hardening temperature of150° C. or smaller and for example a PET film is used for insulativesubstrate 111 of wiring substrate 200, insulative substrate 111 ishardly shrunk by heat.

It should be noted that the melting temperature of conductive adhesiveagent 108 refers to a temperature at which conductive adhesive agent 108starts to be melted, and the hardening temperature of conductiveadhesive agent 108 refers to a temperature at which conductive adhesiveagent 108 starts to be hardened.

As conductive adhesive agent 108, it is preferable to use an Sn—Bi-basedsolder. Sn—Bi-based solder used for conductive adhesive agent 108 ismelted at a low temperature of, for example, approximately 140-150° C.,is therefore processed at a low temperature, is available at aninexpensive price, is easy in handling, and provides a low electricresistance to conductive adhesive agent 108. Here, the Sn—Bi-basedsolder refers to a solder containing Sn and Bi as main components amongmetals constituting the solder, the total mass of Sn and Bi being 90% bymass or greater of the entire mass of the solder.

For better electric characteristics of the solar battery, conductiveadhesive agent 108 preferably has an electric resistivity of 0.001Ω cmor smaller.

In the present invention, as the solar cell, it is preferable to use,for example, a back-side electrode type solar cell configured to haveboth n electrodes and p electrodes formed only on the rear surface of asemiconductor substrate such as a silicon substrate as shown in FIG. 1or FIG. 2. It should be noted that as members constituting the solarcell, for example, conventionally known members can be used.

FIG. 3( a) shows a schematic planar view of one exemplary rear surfaceof the solar cell used in the present invention, On the rear surface ofsilicon substrate 101, n electrodes 106 and p electrodes 107 are formedto have shapes of strips extending in the same direction in the rearsurface of silicon substrate 101 (the left-right direction of the planeof FIG. 3( a)). Such strip-shaped n electrodes 106 and p electrodes 107are arranged alternately one by one in the top-bottom direction of theplane of FIG. 3( a).

FIG. 3( b) shows a schematic planar view of another exemplary rearsurface of the solar cell used in the present invention. On the rearsurface of silicon substrate 101, n electrodes 106 and p electrodes 107are formed to have shapes of dots. In the top-bottom direction andleft-right direction of the plane of FIG. 3( b), such dot-shaped nelectrodes 106 are arranged adjacent to one another and dot-shaped pelectrodes 107 are arranged adjacent to one another. Dot-shaped nelectrodes 106 and dot-shaped p electrodes 107 shown in FIG. 3( b) arearranged in straight lines in the top-bottom direction and left-rightdirection in the plane of FIG. 3( b).

Each of n electrodes 106 and p electrodes 107 on the rear surface of thesolar cell preferably has a shape such as the strip as illustrated inFIG. 3( a) and/or a shape such as the dot as illustrated in FIG. 3( b).In these cases, voids are less likely to be left between the solar celland the wiring substrate upon sealing the solar battery in a sealingmaterial as described below.

FIG. 4 shows a schematic planar view of one exemplary wiring substrateused in the present invention. Here, insulative substrate 111 of wiringsubstrate 200 has a surface provided with wires for n type 109 and wiresfor p type 110 as well as connection electrodes 113 for electricallyconnecting wires for n type 109 and wires for p type 110 to each other.

Further, a busbar p electrode 114 for collecting charges is electricallyconnected to wires for p type 110 provided at one end of insulativesubstrate 111 in the longitudinal direction, whereas a busbar nelectrode 115 for collecting charges is electrically connected to wiresfor n type 109 provided at the other end thereof.

Furthermore, the adhesive agent (not shown) is provided in at least apart of regions on the surface of insulative substrate 111 other thanwires for n type 109, wires for p type 110, connection electrodes 113,busbar p electrode 114, and busbar n electrode 115.

On both busbar p electrode 114 and busbar n electrode 115, slits 112 areprovided to serve as openings for positioning.

It should be noted that in FIG. 4, the respective regions of wires for ntype 109, wires for p type 110, connection electrodes 113, busbar pelectrode 114, and busbar n electrode 115 are divided by dotted linesbut the regions are not limited to those divided as shown in FIG. 4.

Referring to schematic cross sectional views of FIG. 5( a)-FIG. 5( c),one exemplary method for manufacturing the wiring substrate used in thepresent invention will be described below. As shown in FIG. 5( a), on asurface of an appropriate base material 121, hardening resins 122 areapplied. On the surfaces of hardening resins 122, for example,conductive sheets such as copper foils are adhered. Each of theconductive sheets is etched to have a predetermined shape, thus formingwires for n type 109 and wires for p type 110. An exemplary hardeningresin used as each of hardening resins 122 is a conventionally knownhardening resin of a type which loses viscosity by heating and/or UV(ultraviolet radiation).

Next, as shown in FIG. 5( b), base material 121 thus provided with wiresfor n type 109 and wires for p type 110 fabricated as above is attachedand adhered to insulative substrate 111 on which adhesive agent 120 isprovided. Interfaces between hardening resins 122 on base material 121and each of wires for n type 109 and wires for p type 110 are heatedand/or subjected to UV radiation, Accordingly, hardening resins 122 losetheir viscosity, and wires for n type 109 and wires for p type 110 areremoved from hardening resins 122.

Thereafter, as shown in FIG. 5( c), base material 121 is separatedtherefrom to transfer wires for n type 109 and wires for p type 110 toadhesive agent 120 on the surface of insulative substrate 111. In thisway, the wiring substrate can be formed which has a configuration inwhich adhesive agent 120 is exposed in at least a portion of a region onthe surface of insulative substrate 111 other than wires for n type 109and wires for p type 110.

In the description above, depending on a material of adhesive agent 120,hardening resins 122 may he heated and/or subjected to UV radiationbefore base material 121 and insulative substrate 111 are attached andadhered to each other.

Further, base material 121 from which wires for n type 109 and wires forp type 110 have been transferred to adhesive agent 120 is reusable as amember for the solar cell module fabricated by sealing the solar batteryin the sealing material.

FIG. 6 shows a schematic planar view of one exemplary solar battery ofthe present invention, which is fabricated by, for example, installingsolar cells on wiring substrates on which the adhesive agent isprovided. For alignment of the installation locations of solar cells 100on wiring substrates 200, slits 112 may be used.

In an embodiment shown in FIG. 6, in order to electrically connectneighboring two wiring substrates 200 to each other, busbar p electrode114 of one wiring substrate 200 and busbar n electrode 115 of the otherwiring substrate 200 are electrically connected to each other byconductive members 116. Alternatively, for example, there may be adoptedsuch a configuration that does not employ conductive members 116 butallows solar cells 100 to be electrically connected in series naturallywhen placing solar cells 100 on a wiring substrate 200, such as the wirepattern of wiring substrate 200 in an embodiment shown in FIG. 7. Inthis case, insulative substrate 111, which serves as a base material forwiring substrate 200, may be used to also serve as a weather-resistantfilm.

Referring to FIG. 8, another exemplary method for connecting to thewiring substrate will be described. First, as shown in FIG. 8( a), ascreen-printable adhesive agent 120 is pattern-printed on portions ofthe rear surface of solar cell 100 other than the electrodes. Althoughadhesive agent 120 may be printed on the wiring substrate 200 side, itis preferable to print it on the solar cell 100 side due to thefollowing reasons: the electrodes of solar cell 100 can be thinner thanthe wires of wiring substrate 200 and the portions other than theelectrodes therefore have large areas, which makes it easier to printthereon; and it is easier to perform an operation of baking adhesiveagent 120 as solar cell 100 is smaller in size. Then, after bakingadhesive agent 120, as shown in FIG. 8( b), solar cell 100 and wiringsubstrate 200 are placed on each other so that the electrodes of solarcell 100 match with the wires of wiring substrate 200, and are adheredto each other.

Other method than the above can be employed as follows. That is,adhesive agent 120 is applied using a dispenser or the like onto thesurface of insulative substrate 111 on which wires for n type 109 andwires for p type 110 are patterned and/or the rear surface of solar cell100, and then solar cell 100 is placed on wiring substrate 200.

FIG. 9 shows a schematic cross sectional view of one exemplary solarcell module of the present invention, which is fabricated by, forexample, sealing the solar battery in a sealing material. Here, thesolar battery having solar cells 100 placed on wiring substrate 200 issealed in sealing material 125 contained in a container 128 constitutedby a layered film formed by interposing a metal film 127 betweenopposing two insulative films 126. Sealing material 125 has a surfaceprovided with a transparent substrate 124.

As transparent substrate 124, for example, a substrate transparent tosunlight can be used such as a conventionally known glass substrate. Assealing material 125, for example, a resin or the like transparent tosunlight can be used such as a conventionally known EVA (ethylene vinylacetate) resin.

As each of insulative films 126, for example, a conventionally known onecan be used such as a PET film. Further, when container 128 is used asinsulative substrate 111 serving as the base material of wiringsubstrate 200, the insulative substrate of wiring substrate 200 can beused as a weather-resistant film without modification. Further, as metalfilm 127, for example, a conventionally known one can be used such as ametal film of aluminum or the like.

Here, before sealing the solar battery, solar cell 100 is placed onwiring substrate 200. Upon sealing the solar battery, it is preferableto mechanically compress and bond the electrodes of solar cell 100 (nelectrodes 106 and p electrodes 107) and the wires of wiring substrate200 (wires for n type 109 and wires for p type 110). In this way, theelectric connection between the electrodes of solar cell 100 and thewires of wiring substrate 200 can be secured more, thus achievingfurther improved reliability in the connection.

Here, the solar battery can be sealed in sealing material 125 using, forexample, a method including a step of compressing and bonding sealingmaterial 125 and a step of hardening sealing material 125 as follows.First, the above-described solar battery is inserted between sealingmaterial 125 formed on transparent substrate 124 and sealing material125 contained in container 128, and is subjected to vacuum compressionbonding and the like while being heated, thereby compressing and bondingsealing material 125 provided on transparent substrate 124 and sealingmaterial 125 contained in container 128 (step of compressing andbonding). In this way, the solar battery is contained in sealingmaterial 125 filling a space surrounded by transparent substrate 124 andcontainer 128.

Thereafter, sealing material 125 is hardened by further heating or thelike (step of hardening), thus sealing the solar battery configured asabove in sealing material 125 between transparent substrate 124 andcontainer 128. Here, the hardening of sealing material 125 allows theelectrodes of solar cell 100 and the wires of wiring substrate 200 to becompressed and bonded to each other mechanically, thus achieving moresecured electric connection between the electrodes of solar cell 100 andthe wires of wiring substrate 200. In this way, reliability of theconnection is further improved.

Further, fabricating the solar cell module as described above does notrequire a step of applying a conductive adhesive agent and heating it ina reflow furnace. Hence, the number of steps can be reduced, whereby thesolar cell module can be fabricated more easily.

Furthermore, in the case where the electrodes of solar cell 100 and thewires of wiring substrate 200 are connected to each other throughconductive adhesive agent 108 as in the solar battery shown in FIG. 2,it is preferable to use a conductive adhesive agent having a meltingtemperature or hardening temperature of 180° C. or smaller, is morepreferable to use a conductive adhesive agent having a meltingtemperature or hardening temperature of 150° C. or smaller, and isparticularly preferable to use an Sn—Bi-based solder having a meltingtemperature of 150° C. or smaller.

Here, also in the case where the electrodes of solar cell 100 and thewires of wiring substrate 200 are connected to each other throughconductive adhesive agent 108, the solar cell module can be fabricatedby sealing the solar battery in sealing material 125 in the same wayapart from the use of conductive adhesive agent 108.

In the case where a solder is used as conductive adhesive agent 108, thesolder is preferably applied onto the wires of wiring substrate 200and/or the electrodes of solar cell 100 through solder plating orsoaking in a melted solder bath in advance and the electrodes of solarcell 100 and the wires of wiring substrate 200 are then brought intoelectric connection.

Further, in the case where a conductive adhesive agent formed of anSn—Bi-based solder having a melting temperature or hardening temperatureof 180° C. or smaller, more preferably 150° C. or smaller, particularlypreferably having a melting temperature of 150° C. or smaller, is used,the electrodes of solar cell 100 and the wires of wiring substrate 200can be electrically connected to each other with the conductive adhesiveagent interposed therebetween during the step of compressing and bondingand/or the step of hardening, by for example heat generated in the stepof compressing and bonding sealing material 125 and/or the step ofhardening. Further, in this case, the solder has been applied in advanceonto the wires of wiring substrate 200 and/or the electrodes of solarcell 100, thereby preventing production of a gas such as one generatedwhen heating a cream solder. Although an extra step of applyingconductive adhesive agent 108 is added, this method is preferablebecause the electric connection between the electrodes of solar cell 100and the wires of wiring substrate 200 can be more secured by conductiveadhesive agent 108.

As described above, in the case where the solar battery fabricated byelectrically connecting the electrodes of solar cell 100 and the wiresof wiring substrate 200 to each other is sealed in the sealing materialto fabricate the solar cell module, the solar battery can be protectedfrom application of heat, apart from heat generated while fixing them byadhesive agent 120 at a normal temperature as well as heat in the stepof compressing and bonding sealing material 125 and/or in the step ofhardening. This can reduce stress conventionally generated due to adifference in thermal expansion coefficient between a solar cell and awire material of a wiring substrate. Accordingly, the solar cell can beprevented from being cracked, thus obtaining a thinner solar cell.Furthermore, influence of thermal stress during an actual operation ofthe solar cell module can be reduced too.

In addition, in order to prevent water vapor from entering the solarcell module, it is preferable to use a container 128 including amoisture penetration preventing layer such as metal film 127 formed ofaluminum or the like which is greatly effective to prevent penetrationof water vapor, as shown in the embodiment of FIG. 9. Entrance of watervapor into the solar cell module is likely to cause corrosion atinterfaces between the electrodes of solar cell 100 and the wires ofwiring substrate 200, or corrosion of conductive adhesive agent 108provided between the electrodes of solar cell 100 and the wires ofwiring substrate 200 (particularly, corrosion of the Sn—Bi-basedsolder). Hence, by using container 128 including the above-describedmoisture penetration preventing layer, the corrosion can be preventedeffectively, thus achieving improved long-term reliability of the solarcell module.

As container 128 including the moisture penetration preventing layer,for example, as shown in the embodiment of FIG. 9, it is preferable touse a layered film in which metal film 127 formed of aluminum isinterposed between insulative films 126 each formed of PET. For example,by covering the portions other than transparent substrate 124 with thelayered film as shown in FIG. 9, water vapor can be effectivelyprevented from entering the solar cell module. For a portion, such as anend surface of the solar cell module, with which it is difficult for thelayered film to be in intimate contact, a moisture penetrationpreventing tape such as a butyl rubber tape can be used to achievecomplete intimate contact.

Thereafter, the wiring substrate of the above-described solar cellmodule and a terminal box may be connected using a conductive member,and the solar cell module may be fit in and surrounded by a frame bodymade of aluminum or the like.

EXAMPLES Example 1

First, back-side electrode type solar cells each having a rear surfaceformed as shown in FIG. 3( a) were fabricated using a conventionallyknown method. Each solar-cell 100 was configured so that strip-shaped nelectrodes 106 and p electrodes 107 were arranged alternately one by oneon the rear surface of n type silicon substrate 101 having alight-receiving surface and a rear surface both having a shape of squarewith each side of 100 mm.

Then, the method shown in FIG. 5( a)-FIG. 5( c) was employed to transferwires made of copper to an adhesive agent 120 provided on an insulativesubstrate 111 made of PET. In this way, a wiring substrate 200 wasfabricated. As adhesive agent 120, an acrylic-based viscous adhesiveagent was used.

Then, as shown in FIG. 7, sixteen solar cells 100 were placed on onewiring substrate 200. In this way, a solar battery was fabricated inwhich solar cells 100 were fixed onto wiring substrate 200 by adhesiveagent 120. In fabricating the solar battery, n electrodes 106 of each ofsixteen solar cells 100 were placed on wires for n type 109 of wiringsubstrate 200 and p electrodes 107 of each solar cell 100 were placed onwires for p type 110 of wiring substrate 200, while using slits 112 ofwiring substrate 200 as alignment marks for alignment thereof.

Thereafter, the solar battery fabricated as described above was sealedin a sealing material to fabricate a solar cell module as shown in FIG.9. In fabricating the solar battery, the solar battery was interposedbetween a sealing material 125 made of an EVA resin and formed on atransparent substrate 124 constituted by a glass substrate and a sealingmaterial 125 made of an EVA resin and contained in a container 128constituted by a layered film in which a metal film 127 made of aluminumwas interposed between insulative films 126 made of PET, was thereaftersubjected to vacuum thermo-compression bonding to compress and bondsealing material 125 provided on transparent substrate 124 and sealingmaterial 125 contained in container 128 (step of compressing andbonding), and thereafter sealing materials 125 were hardened by heating(step of hardening).

The step of compressing and bonding was performed by placing, on sealingmaterial 125 contained in container 128, sealing material 125 formed ontransparent substrate 124, and retaining them for seven minutes at 140°C. while evacuating it.

The step of hardening was performed after the step of compressing andbonding, by heating sealing materials 125 at 145° C. for 40 minutes toharden sealing materials 125 each made of an EVA resin. In this way, theelectrodes of each solar cell 100 and the wires of wiring substrate 200are in further intimate contact with each other.

Thereafter, the solar cell module fabricated as described above wasconnected to a terminal box, and was fit in and surrounded by a framebody made of aluminum.

By fabricating a solar module as described above, there can befabricated a solar cell module having a solar battery, which is sealedtherein and in which electrodes of a solar cell and wires of a wiringsubstrate are electrically connected to each other at a low temperaturereadily to attain highly reliable connection therebetween and relativelygood electric characteristics. In addition, as insulative substrate 111,an inexpensive PET can be used. Furthermore, it can be fabricatedwithout application of a conductive adhesive agent and heating with areflow furnace, thus achieving reduction of the number of steps.

Example 2

First, back-side electrode type solar cells each having a rear surfaceformed as shown in FIG. 3( a) were fabricated using a conventionallyknown method. Each solar cell 100 was configured so that strip-shaped nelectrodes 106 and p electrodes 107 were arranged alternately one by oneon the rear surface of n type silicon substrate 101 having alight-receiving surface and a rear surface both having a shape of squarewith each side of 100 mm, Each of the solar cells was soaked in an Sn—Bisolder bath to coat the electrode portions with the solder.

Then, as shown in FIG. 8( a), an acrylic-based viscous adhesive agentwas applied to a portion of the rear surface of the solar cell otherthan the electrodes provided thereon, by means of screen printing.Thereafter, it was baked at 100° C., thus exhibiting viscosity of theviscous adhesive agent.

Then, as shown in FIG. 7, sixteen solar cells 100 were placed on onewiring substrate 200. In this way, a solar battery was fabricated inwhich solar cells 100 were fixed onto wiring substrate 200 by adhesiveagent 120. In fabricating the solar battery, n electrodes 106 of each ofsixteen solar cells 100 were placed on wires for n type 109 of wiringsubstrate 200 and p electrodes 107 of each solar cell 100 were placed onwires for p type 110 of wiring substrate 200, while using slits 112 ofwiring substrate 200 as alignment marks for alignment thereof.

Because a layered film in which a metal film 127 made of aluminum wasinterposed between insulative films 126 each made of PET had beenadopted in advance for the base material of wiring substrate 200, an EVAresin sheet and a glass substrate were provided on the solar batteryhaving solar cells 100 fixed onto wiring substrate 200, Such a solarbattery was then retained at 140° C. for seven minutes while beingevacuated and thereafter was heated at 145° C. for 40 minutes to hardenthe EVA, thereby compressing, bonding, and sealing the solar battery tofabricate a solar cell module.

Through the above-described step of heating, the solder provided inadvance to coat the electrodes of the solar cell was melted to connectthe electrodes of the solar cell and the wires of the wiring substratesto each other, thus achieving more reliable connection therebetween.

Thereafter, the solar cell module fabricated as described above wasconnected to a terminal box, and was fit in and surrounded by a framebody made of aluminum.

It should be considered that the embodiments and examples disclosedherein are illustrative and non-restrictive in any respect. The scope ofthe present invention is defined by the scope of claims, and is intendedto include any modifications within the scope and meaning equivalent tothe terms of the claims.

INDUSTRIAL APPLICABILITY

According to the present invention, there can be provided a solarbattery in which electrodes of a solar cell and wires of a wiringsubstrate can be electrically connected to each other at a lowtemperature readily to attain highly reliable connection therebetweenand relatively good electric characteristics; a method for manufacturingthe solar battery; a method for manufacturing a solar cell module usingthe solar battery; and the solar cell module.

1. A solar battery comprising: a solar cell; a wiring substrate; and anadhesive agent for adhering said solar cell and said wiring substrate toeach other; and wherein said wiring substrate includes an insulativebase material and a wire of a conductive material formed on saidinsulative base material, and wherein said adhesive agent is disposed onat least a part of a region of said insulative base material other thana region in which said wire is formed.
 2. (canceled)
 3. The solarbattery according to claim 1, wherein said insulative base materialincludes at least one of polyethylene terephthalate and polyethylenenaphthalate.
 4. (canceled)
 5. The solar battery according to claim 1,wherein said wire is formed of a material including at least oneselected from a group consisting of copper, aluminum, and silver.
 6. Thesolar battery according to claim 1, wherein said adhesive agent includesat least one selected from a group consisting of a silicone-basedadhesive agent, an acrylic-based adhesive agent, an epoxy-based adhesiveagent, and a rubber-based adhesive agent.
 7. The solar battery accordingto claim 1, wherein said adhesive agent has stable adhesiveness evenwhen exposed to an environment at a temperature of 150° C. or greater.8. The solar battery according to claim 1, wherein said adhesive agentis a viscous adhesive agent.
 9. The solar battery according to claim 1,wherein said solar cell is a back-side electrode type solar cell. 10.The solar battery according to claim 9, wherein an electrode of saidsolar cell has a shape of at least one of a strip and a dot.
 11. Thesolar battery according to claim 1, wherein an electrode of said solarcell and said wire of said wiring substrate are electrically connectedto each other via a conductive adhesive agent.
 12. The solar batteryaccording to claim 11, wherein said conductive adhesive agent has amelting temperature/hardening temperature of 180° C. or smaller. 13.(canceled)
 14. (canceled)
 15. A method for manufacturing the solarbattery as recited in claim 1, comprising: disposing said wire on aviscous adhesive layer disposed on a base material; disposing said wire,disposed on said viscous adhesive layer, on said adhesive agent disposedon said insulative base material; forming said wiring substrate byremoving said wire from said viscous adhesive layer to transfer saidwire onto said adhesive agent; and adhering said solar cell and saidwiring substrate to each other by said adhesive agent.
 16. A method formanufacturing the solar battery as recited in claim 1, comprising:disposing said adhesive agent on at least a part of a region of saidsolar cell other than a region in which a electrode of said solar cellis formed; and adhering said solar cell and said wiring substrate usingsaid adhesive agent.
 17. (canceled)
 18. A method for manufacturing asolar cell module in which the solar battery as recited in claim 1 issealed in a sealing material, wherein when sealing said solar battery,an electrode of said solar cell and said wire of said wiring substrateare mechanically compressed and bonded.
 19. (canceled)
 20. A solar cellmodule in which the solar battery as recited in claim 1 is sealed in asealing material, wherein said sealing material is contained in acontainer having, on at least one of its bottom portion and its sidewall, a moisture penetration preventing layer for preventing penetrationof moisture.
 21. The solar battery according to claim 1, wherein saidwiring substrates are electrically connected to each other by aconductive member.